MCBA Water Treatment Knowledge Hub

Storm overflow register · 2025 annual return

Southern Water storm overflows, 2025

Southern Water reported 977 storm overflows in England for 2025. Together they recorded 15,554 spills over 114,868 hours, an average of 15.9 spills per overflow against 20.4 across England. That ranks 4 of 10 companies, where 1 is the fewest spills per overflow. Counting the same overflows in both years, spills were down 47% on 2024.

175 overflows did not spill · 42 spilled more than 60 times · 862 had monitors working for 90% of the year or more · 215 sewage treatment works with overflows

Hours spilling by month, 2025

010k20k30k40kJan 2025: 38,729 hours spillingJanFeb 2025: 17,875 hours spillingFebMar 2025: 4,010 hours spillingMarApr 2025: 1,990 hours spillingAprMay 2025: 746 hours spillingMayJun 2025: 804 hours spillingJunJul 2025: 2,044 hours spillingJulAug 2025: 883 hours spillingAugSep 2025: 4,161 hours spillingSepOct 2025: 8,831 hours spillingOctNov 2025: 6,321 hours spillingNovDec 2025: 28,488 hours spillingDec
Hours spilling, all Southern Water overflows, from the start/stop records. Spills running across a month end are split between the months.

All Southern Water storm overflows

Sorted by hours spilling. Open an overflow for its permit, location, reasons for high spills and improvement status.

OverflowDischarges toSpills 2025Hours 2025Spills vs 2024Monitor uptime
Sutton Valence WwTW
Storm tank at sewage works
Sewage works
Sutton Valence
Company site name
SUTTON VALENCE SSO - 115909
EA ID / permit
SWS00842 · W00481
Outlet location
TQ8093048090 (OS grid reference) · View on Apple Maps
WFD catchment
Tributary of Beult at Sutton Valance (GB106040018040)
2024 spills / hours
2 / 14
Long-term average
1.0 spills a year (monitored since 2019)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Trib of the River Beult 0 0.0 down 100% 98%
Teynham S.T.W.
Storm tank at sewage works
Sewage works
Teynham S T W
Company site name
TEYNHAM SSO - 115446
EA ID / permit
SWS00858 · W00577
Outlet location
TQ9563063920 (OS grid reference) · View on Apple Maps
WFD catchment
SWALE (GB530604011500)
Shellfish water
Swale Central
2024 spills / hours
0 / 0.0
Long-term average
1.6 spills a year (monitored since 2016)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Frognal Drain 0 0.0 no change 99%
The Anchorage Gosport Ceo
Storm discharge at pumping station
Company site name
THE ANCHORAGE GOSPORT CEO - 108857
EA ID / permit
SWS00859 · A01371
Outlet location
SZ6153099470 (OS grid reference) · View on Apple Maps
WFD catchment
PORTSMOUTH HARBOUR (GB580705140000)
Bathing water
Southsea East; Stokes Bay
Shellfish water
Central Solent; Portsmouth Harbour; Ryde; Spithead and Stokes Bay
2024 spills / hours
3 / 5.5
Long-term average
0.7 spills a year (monitored since 2016)
Investigation
Bathing Water and/or Shellfish Water investigation ongoing
Improvement
No improvement action in reporting period
 Portsmouth Harbour 0 0.0 down 100% 100%
The Hundred Romsey CSO
Overflow on sewer network
Company site name
THE HUNDRED ROMSEY CSO - 110233
EA ID / permit
SWS00862 · A01446
Outlet location
SU3551020990 (OS grid reference) · View on Apple Maps
WFD catchment
Tadburn Lake (GB107042016490)
2024 spills / hours
4 / 11
Long-term average
2.2 spills a year (monitored since 2019)
Monitor below 90%
Sensor failure / issue · Resolved - Jun
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Tadburn Lake 0 0.0 down 100% 53%
The Warren P.S.
Storm discharge at pumping station
Company site name
THE WARREN MAYFIELD CEO - 108360
EA ID / permit
SWS00868 · W02514
Outlet location
TQ5960026720 (OS grid reference) · View on Apple Maps
WFD catchment
Upper Rother, Coggins Mill to Five Ashes (GB107040013490)
2024 spills / hours
1 / 0.4
Long-term average
2.7 spills a year (monitored since 2019)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Tributary of the River Rother 0 0.0 down 100% 100%
Tottington Drive Small Dole Ceo
Storm discharge at pumping station
Company site name
TOTTINGTON DRIVE SMALL DOLE CEO - 108366
EA ID / permit
SWS00878 · A01008
Outlet location
TQ2143012990 (OS grid reference) · View on Apple Maps
WFD catchment
Woodsmill Stream (GB107041012060)
2024 spills / hours
0 / 0.0
Long-term average
0.7 spills a year (monitored since 2016)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Unnamed Trib of River Adur 0 0.0 no change 100%
Tovil Wharf Wastewater PS
Storm discharge at pumping station
Company site name
TOVIL WHARF CEO - 108856
EA ID / permit
SWS00879 · A01330
Outlet location
TQ7512054830 (OS grid reference) · View on Apple Maps
WFD catchment
Medway at Maidstone (GB106040018440)
2024 spills / hours
0 / 0.0
Long-term average
0.1 spills a year (monitored since 2016)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 The River Medway 0 0.0 no change 100%
Town Pier, Gravesend CSO
Other storm discharge asset type
Company site name
TOWN PIER GRAVESEND CSO - 116068
EA ID / permit
SWS00881 · D00076
Outlet location
TQ6452074450 (OS grid reference) · View on Apple Maps
WFD catchment
THAMES MIDDLE (GB530603911402)
2024 spills / hours
0 / 0.0
Long-term average
20.1 spills a year (monitored since 2016)
Investigation
UWWTR investigation ongoing
Improvement
No improvement action in reporting period
 Thames Estuary 0 0.0 no change 100%
Victoria Road Ashford CSO
Overflow on sewer network
Company site name
VICTORIA ROAD ASHFORD CSO - 108751
EA ID / permit
SWS00900 · D01033
Outlet location
TR0075042310 (OS grid reference) · View on Apple Maps
WFD catchment
Upper Great Stour (GB107040019660)
2024 spills / hours
0 / 0.0
Long-term average
0.2 spills a year (monitored since 2019)
Monitor below 90%
Sensor failure / issue · Scheduled
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Trib of the Great Stour 0 0.0 no change 77%
Victoria Road Netley Ceo
Storm discharge at pumping station
Company site name
VICTORIA ROAD NETLEY CEO - 107372
EA ID / permit
SWS00901 · A01372
Outlet location
SU4564008080 (OS grid reference) · View on Apple Maps
WFD catchment
SOUTHAMPTON WATER (GB520704202800)
Shellfish water
Southampton Water; Approaches to Southampton Water
2024 spills / hours
0 / 0.0
Long-term average
0.0 spills a year (monitored since 2016)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Southampton Water 0 0.0 no change 100%
Wallington Hill CSO
Overflow on sewer network
Company site name
WALLINGTON HILL FAREHAM CSO - 108494
EA ID / permit
SWS00906 · H01049
Outlet location
SU5833006720 (OS grid reference) · View on Apple Maps
WFD catchment
R. Wallington (GB107042016360)
Shellfish water
Portsmouth Harbour
2024 spills / hours
0 / 0.0
Long-term average
0.0 spills a year (monitored since 2016)
Investigation
Env Act (SODRP) investigation ongoing
Improvement
Env Act (SODRP) improvement ongoing, Bathing Water and/or Shellfish Water improvement ongoing
 River Wallington 0 0.0 no change 100%
Water Lane/Arundel Road
Storm discharge at pumping station
Company site name
WATER LANE LITTLEHAMPTON CEO - 108013
EA ID / permit
SWS00912 · A00862
Outlet location
TQ0263002720 (OS grid reference) · View on Apple Maps
WFD catchment
Black Ditch (GB107041012890)
Bathing water
Littlehampton
2024 spills / hours
0 / 0.0
Long-term average
0.5 spills a year (monitored since 2019)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Freshwater River 0 0.0 no change 100%
Wells Close Whiteley Ceo
Storm discharge at pumping station
Company site name
WELLS CLOSE WHITELEY CEO - 110314
EA ID / permit
SWS00916 · A01394
Outlet location
SU5223010050 (OS grid reference) · View on Apple Maps
WFD catchment
SOUTHAMPTON WATER (GB520704202800)
Shellfish water
Approaches to Southampton Water
2024 spills / hours
0 / 0.0
Long-term average
0.0 spills a year (monitored since 2017)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Burridge Stream 0 0.0 no change 100%
Wessex Lane Southampton
Overflow on sewer network
Company site name
WESSEX LANE SOUTHAMPTON OUTSIDE 1 CSO - 108497
EA ID / permit
SWS00917 · H01796
Outlet location
SU4403016020 (OS grid reference) · View on Apple Maps
WFD catchment
Monks Brook (GB107042016310)
Shellfish water
Southampton Water
2024 spills / hours
1 / 1.5
Long-term average
0.4 spills a year (monitored since 2016)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Saline Estuary 0 0.0 down 100% 97%
Wessex Lane Southampton Outside 15
Overflow on sewer network
Company site name
WESSEX LANE SOUTHAMPTON OUTSIDE 15 CSO - 108495
EA ID / permit
SWS00919 · H01794
Outlet location
SU4401015990 (OS grid reference) · View on Apple Maps
WFD catchment
Monks Brook (GB107042016310)
Shellfish water
Southampton Water
2024 spills / hours
1 / 1.3
Long-term average
0.4 spills a year (monitored since 2016)
Monitor below 90%
Sensor failure / issue · Resolved - Oct
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Saline Estuary 0 0.0 down 100% 79%
West Common Road Fawley Ceo
Storm discharge at pumping station
Company site name
WEST COMMON FAWLEY CEO - 108890
EA ID / permit
SWS00921 · A01272/H
Outlet location
SU4444000990 (OS grid reference) · View on Apple Maps
WFD catchment
Dark Water (GB107042011330)
Bathing water
Lepe
Shellfish water
Approaches to Southampton Water; Beaulieu River; Cowes and Medina; Lepe Middle Bank; Stanswood Bay
2024 spills / hours
1 / 0.2
Long-term average
0.1 spills a year (monitored since 2016)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Dark Water 0 0.0 down 100% 98%
Westbrook Grove Purbrook Ceo
Storm discharge at pumping station
Company site name
WESTBROOK GROVE PURBROOK CEO - 108498
EA ID / permit
SWS00928 · A01278
Outlet location
SU6758007880 (OS grid reference) · View on Apple Maps
WFD catchment
Potwell Trib (GB107042016400)
Shellfish water
Langstone Harbour; Portsmouth Harbour
2024 spills / hours
0 / 0.0
Long-term average
0.8 spills a year (monitored since 2016)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Wallington River via Drain 0 0.0 no change 100%
Whiteley Wps
Storm discharge at pumping station
Company site name
WHITELEY LANE WHITELEY CEO - 108854
EA ID / permit
SWS00939 · A01127
Outlet location
SU5347009630 (OS grid reference) · View on Apple Maps
WFD catchment
R. Meon (GB107042016640)
2024 spills / hours
0 / 0.0
Long-term average
0.0 spills a year (monitored since 2016)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Curbridge Stream 0 0.0 no change 100%
Whiteparish WwTW
Storm tank at sewage works
Sewage works
Whiteparish
Company site name
WHITEPARISH SSO - 115449
EA ID / permit
SWS00940 · W00238
Outlet location
SU2411022540 (OS grid reference) · View on Apple Maps
WFD catchment
Whiteparish Trib (GB107042016440)
2024 spills / hours
0 / 0.0
Long-term average
1.8 spills a year (monitored since 2016)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Trib of River Blackwater 0 0.0 no change 100%
Whitewall Creek WwTW
Storm tank at sewage works
Sewage works
Whitewall Creek
Company site name
WHITEWALL CREEK SSO - 115854
EA ID / permit
SWS00941 · W00510
Outlet location
TQ7517069900 (OS grid reference) · View on Apple Maps
WFD catchment
MEDWAY (GB530604002300)
2024 spills / hours
4 / 28
Long-term average
2.6 spills a year (monitored since 2016)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Whitewall Creek 0 0.0 down 100% 100%
Wigmore Road
Overflow on sewer network
Company site name
WIGMORE ROAD WORTHING OUTSIDE 16 CSO - 108381
EA ID / permit
SWS00947 · A00964
Outlet location
TQ1592004050 (OS grid reference) · View on Apple Maps
WFD catchment
Teville Stream (GB107041011940)
Bathing water
Lancing, Beach Green; Worthing; Worthing Beach House
2024 spills / hours
0 / 0.0
Long-term average
0.2 spills a year (monitored since 2016)
Investigation
Bathing Water and/or Shellfish Water investigation ongoing
Improvement
No improvement action in reporting period
 A Trib. of the Teville Stream 0 0.0 no change 100%
Winford Ceo
Storm discharge at pumping station
Company site name
WINFORD CEO - 108570
EA ID / permit
SWS00956 · A00231
Outlet location
SZ5581084150 (OS grid reference) · View on Apple Maps
WFD catchment
Eastern Yar (Lower) (GB107101005971)
2024 spills / hours
12 / 126
Long-term average
5.1 spills a year (monitored since 2018)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Drain to River Yar 0 0.0 down 100% 100%
Woolston WwTW
Inlet overflow at sewage works
Sewage works
Woolston
Company site name
WOOLSTON EMO - 115451
EA ID / permit
SWS00968 · A00856
Outlet location
SU4339010440 (OS grid reference) · View on Apple Maps
WFD catchment
SOUTHAMPTON WATER (GB520704202800)
Shellfish water
Southampton Water
2024 spills / hours
1 / 0.4
Long-term average
2.7 spills a year (monitored since 2016)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 River Itchen Estuary 0 0.0 down 100% 99%
Worthing WwTW
Inlet overflow at sewage works
Sewage works
Worthing
Company site name
EAST WORTHING CEO - 115406
EA ID / permit
SWS00970 · A01107
Outlet location
TQ1716002080 (OS grid reference) · View on Apple Maps
WFD catchment
Sussex (GB640704540003)
Bathing water
Lancing, Beach Green; Worthing; Worthing Beach House
2024 spills / hours
1 / 4.2
Long-term average
0.2 spills a year (monitored since 2016)
Investigation
Bathing Water and/or Shellfish Water investigation ongoing
Improvement
No improvement action in reporting period
 English Channel 0 0.0 down 100% 99%
Poynings WwTW, Brighton
Storm tank at sewage works
Sewage works
Poynings Brighton
Company site name
POYNINGS SSO - 116295
EA ID / permit
SWS00979 · A01216
Outlet location
TQ2587112331 (OS grid reference) · View on Apple Maps
WFD catchment
Woodsmill Stream (GB107041012060)
2024 spills / hours
0 / 0.0
Long-term average
2.5 spills a year (monitored since 2021)
Investigation
Env Act (SODRP) investigation ongoing
Improvement
No improvement action in reporting period
 Adjacent Stream. Trib.R.Adur 0 0.0 no change 100%
Yalding Old Works Ceo
Storm discharge at pumping station
Company site name
YALDING OLD WORKS SSO - 115964
EA ID / permit
SWS00980 · A00268
Outlet location
TQ6911050420 (OS grid reference) · View on Apple Maps
WFD catchment
Medway at Maidstone (GB106040018440)
2024 spills / hours
0 / 0.0
Long-term average
0.0 spills a year (monitored since 2019)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 Trib of the River Medway 0 0.0 no change 100%
Detling Close Gillingham Ceo
Overflow on sewer network
Company site name
DETLING CLOSE GILLINGHAM CEO - 116201
EA ID / permit
SWS00981 · Unpermitted
Outlet location
TQ8138967925 (OS grid reference) · View on Apple Maps
WFD catchment
MEDWAY (GB530604002300)
2024 spills / hours
0 / 0.0
Long-term average
0.0 spills a year (monitored since 2023)
Investigation
No investigation activity in reporting period
Improvement
No improvement action in reporting period
 The Medway Estuary 0 0.0 no change 99%

Sewage treatment works

Storm tanks and inlet overflows at each Southern Water sewage works. The figures are 2025 spills.

← All water companies · Contains Environment Agency data licensed under the Open Government Licence v3.0. How to read the data.